Way cool! YES!
Michael McGrady
Craig McClanahan wrote:
On Mon, 18 Oct 2004 10:48:50 -0400, Sean Schofield
<[EMAIL PROTECTED]> wrote:
Craig McClanahan wrote:
I prefer to use them throughout, so we have the opportunity to not synchronize in
cases where thread safety is not an issue -- it is here, though.
OK makes sense.
More subtly, though, you'll also note that I use Map instead of
HashMap to declare the actual instance variable, and the return values
from appropriate methods. That way, the actual implementation class
could be specialized later without breaking method signatures. That's
not as easy to do if you're throwing Hashtables around (any
specialized version would have to subclass Hashtable, and not some
more generic interface).
This makes sense in general but I don't see how it applies in this
specific case. Only the instance variable is a Map. There aren't any
public methods in CatalogFactory that return Map so how does this help
with subclassing? I'm just wondering ... I'm not proposing changing it
back.
That is true for now, but I've seen many projects (including a couple
of my own) get bit by adding public accessors later on --
PropertyUtils.getMappedPropertyDescriptors() returns FastHashMap
instead of Map and we didn't catch it quick enough :-(.
Finally, I also just noticed that you implemented getInstance() in
CatalogFactory and had it return an instance of CatalogBase. Did you
change your mind on this? Is this because it will be easier to manage
class loader issues in the factory?
Not just easier ... the original strategy I suggested would never
eliminate the reference to the class loader in the clear() method, so
the garbage collection problems I spoke of would still happen. Now,
clear() -- which is also on CatalogFactory -- throws away its own
reference to the class loader and any loaded catalogs.
I'm assuming that your reasoning for having CatalogFactoryBase is so
that we (or end user) can change the implementation of CatalogFactory
without affecting users code. Right now user's can't really specify
their own CatalogFactory. I'm fine with this, but just checking to see
if this was your reasoning.
Yep, that's the reasoning -- future proofing the fundamental APIs a
little. We've had to go back and try to do this thing in other
scenarios where static utility classes were defined but couldn't be
replaced. Now, all we'd need to do if the need came up is add a way
to register your own CatalogFactory implementation class in order to
create instances, if the need ever comes up.
The end result of all this, by the way, is quite sweet ... no need to
pass around references to a Catalog or a CatalogFactory, and it works
even if [chain] is installed in a shared directory. You'll be able to
see this too once you update your CVS checkout to pick up the
ConfigCatalogRule.java file that I just checked in :-).
sean
Craig
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